A 14-year-old schoolgirl was found hanged after developing an eating disorder following playground taunts about her weight, an inquest was told.

Fiona Geraghty began to suffer from bulimia after schoolmates at Kings College in Taunton, Somerset, teased her about her size, the inquest heard. The girl's mother, Elspeth Geraghty, a GP, criticised the care Fiona had received from mental health professionals and the way the school reacted to her daughter's plight.

Police were called to the family home at Nailsbourne, near Taunton, at around 7am on 14 July last year after Fiona, described by her headmaster as "charming, talented and lively girl", was found hanged.

Her mother told the inquest that Fiona had started at the school in September 2010 but had difficulty settling. "Fiona did have some relationship issues with girls in her peer group," she said. "Fiona appeared to have a real fear of puberty and the fear of growing into a woman. Fiona had a very poor body image."

Geraghty said she was alerted to the possibility her daughter was suffering from bulimia when she was contacted by Fiona's housemistress in February last year and told the teenager had been spotted vomiting. Fiona informed her mother that she had been taunted about her size and she was taken to see her GP.

The girl was referred by the family doctor to the child and adolescent mental health services in Taunton. The letter from Fiona's GP to CAMHS stated explicitly that she had said she had been taunted over her weight.

She saw Ross Gillanders, a community psychiatric nurse, four times in April and May before being discharged.

Elspeth Geraghty said: "Fiona was a clever girl and I believe she would have told Ross Gillanders what she felt he wanted to hear." She said she thought that Gillanders and the CAMHS service was "naive" and her daughter should have been seen by a child psychiatrist.

She added: "I feel let down by the mental health services. I believe eating disorders such as this suffered by Fiona are as the result of an underlying psychiatric problem. Being seen on four occasions before being discharged seems an wholly inappropriate response."

Geraghty said her daughter, nicknamed "Yo-Yo" because of her bouncy personality, had written a school essay in which she spoke of her health problems and "self-loathing". She said she was disappointed with aspects of the college's response. "There was no real concern or significance placed on the events in that term," she said.

The inquest heard that Fiona loved horses and was sporty but had been sidelined because of a knee injury. Ross Gillanders told the inquest that Fiona presented as someone suffering from "disordered eating" rather than an eating disorder. He said Fiona told him: "I am not wanted" by members of her peer group and had said she thought she would be accepted if she had been slimmer.

Gillanders said she was going to be moving schools and was looking forward to the change. He defended the decision to discharge Fiona. "She didn't want to engage with the service and I had to think about the long term. I didn't want to put her off therapy," he said. Gillanders judged there was a "low risk" of her committing suicide.

But Dr Bryan Lask, a professor of child and adolescent psychiatry at Great Ormond Street hospital in London, criticised the decision to discharge Fiona.

"I do not think her full clinical picture could be evident after just four sessions," Lask said. "There was insufficient information about what was happening in her life … There was insufficient evidence of improvement to justify her discharge.

The court heard that shortly before her death Fiona, whose father David is a histopathologist, got into trouble with her parents over postings on Facebook and her laptop had been confiscated.

Kings College released a statement praising Fiona. Headmaster Richard Biggs said: "Fiona was a charming, talented and lively girl who lit up our school. She is deeply missed by her many friends here." The school will comment further when the inquest at West Somerset coroners court concludes.